Described below is a method for setting up a non-wired network by determining and utilizing local topology information.
The wire-based network topology for transmitting data between a plurality of communication devices is associated with loss of mobility and therefore loss of convenience. By contrast, network technology which is not wire-based allows data to be transmitted over short distances without being subject to limitations in terms of mobility. In addition to this, the communication devices can connect spontaneously and autonomously.
In a first method, a first communication device initially receives a list specifying the further communication devices to which it can connect. By advancing progressively through the list or by manual manipulation, the first communication device decides which further communication device it should ask to set up a connection.
In a second method (Specification of the Bluetooth System, Version 1.2, Core) for setting up a non-wired network, a distinction relating to communication devices is made between a communication control device which is responsible for the control of the communication and a communication device which is controlled by the communication control device. Two communication control devices or two controlled communication devices cannot generally connect to each other. The number of communication devices which can be controlled by a communication control device can be limited by technical and/or administrative measures. If a communication control device can only control a limited number of communication devices, this means that the size of a network is restricted by the subscriber capacity of its communication control device. A larger number of communication devices can be achieved by combining individual networks to form a larger overall network. There are two possibilities for creating the required bridge connection between two communication control devices. One possibility is for a device to function as a communication control device in the first network and as a controlled communication device in the second network. Another possibility is to connect two communication control devices via a controlled communication device. Various network topologies can be obtained in this context, e.g. tree-type, chain-type or mesh-type topologies.
In one implementation of a non-wired network according to the second method at the Technion-Israel Institute of Technology in Haifa, information indicating whether it is to operate as a communication control device or as a controlled communication device is required from each device when it starts. Various topologies can then be generated on the basis of the positioning and the sequence in which the devices are switched on (www-comnet.technion.ac.il/˜cn9w02). Such a network having a tree topology has been set up at the ETH in Zurich (www.tik.ee.ethz.ch/˜beutel/bt_node.html). The formation algorithm is not known in greater detail.
This method has a disadvantage in that no information concerning the local topology of the network is available to a communication device desiring to set up a connection. As a consequence, it is possible that an individual communication device or whole subnetworks are not integrated into the overall network. Furthermore, the setup of a network can only be achieved statically and therefore does not satisfy the dynamic requirements in the case of non-wired transmission involving a plurality of communication devices.
The problem addressed is that of specifying a method by which an overall network formed by a plurality of communication devices can organize itself, and individual communication devices and/or subnetworks which are not yet connected are included when this network is set up.
An essential aspect is the determining of the local topology information. In accordance with the method described below, this is achieved by a message exchange between the communication devices. To this end, a first communication device sends a query message containing a list of identification codes of further communication devices, to which a connection can be set up, to second communication devices which are connected to the first communication device. At least one second communication device, wherein a connection exists between the second communication device and one of the further communication devices identified in the query message and/or wherein the second communication device is itself a communication device identified in the query message, sends a reply message to the first communication device. From the reply message, it is possible to determine the identification codes of the further communication devices which are connected to the second communication device and/or to extract the identification code of the second communication device if this is itself a communication device identified in the query message.
The first communication device requests the setting up of a connection to at least one further communication device which is identified in the query message and to which no connection exists from a second communication device. A successful request results in a connection setup.
Without restricting the generality of this term, communication devices are understood to include PCs and computer peripheral devices, mobile devices (laptops, handheld PCs, PDAs), telecommunication devices (mobile phones, ISDN installations), video and TV devices, audio devices and domestic appliances (washing machines, refrigerators), for example. These devices can be networked using IrDA, Bluetooth or WLAN modules, for example.